1. Field of the Invention
The present invention relates to a tunable anti-Stokes Raman laser, and more particularly, to a tunable anti-Stokes Raman laser capable of generating vacuum ultraviolet (VUV) stimulated radiation by creating a metastable population inversion of an alkali halide through selective photodissociation.
2. Description of the Prior Art
In previous experiments, nonresonant anti-Stokes superfluorescence has been observed, and efficiency studies of the anti-Stokes Raman laser have been reported by J. C. White et al in an article entitled "Anti-Stokes Raman Laser" appearing in Physical Review A, February 1982. In those studies, a metastable T1*(6p.sup.2 p.degree..sub.3/2) population inversion was utilized to Taman up-convert visible and near ultraviolet lasers into the 270-380 nm range.
An article entitled "Observation of Stimulated Anti-Stokes Raman Scattering in Inverted Atomic Iodine" by R. L. Carman et al in Physical Review Letters, Vol. 33, No. 4 at pp. 190-3 reports the measurement of anti-Stokes Raman gain from an inverted population in atomic iodine, where the population inversion was achieved by flash photolysis of trifluromethyliodide (CF.sub.3 I). The anti-Stokes Raman signal was observed by pumping this inversion with the fundamental of a Nd:YAG laser at 1.06 .mu.m and probing the gain with a broadband dye laser. However, superfluorescent emission at the non-resonant anti-Stokes wavelength was not observed.
The dynamics of photodissociation of alkali halide systems into dipole allowed transistions has been studied extensively. One result of these studies, as disclosed in an article entitled "Inversion of the Na Resonance Line by Selective Photodissociation of NaI" by J. C. White appearing in Applied Physics Letters, Vol. 33, No. 4, Aug. 15, 1978 at pp. 325-327, is that the alkali halides absorb ultraviolet radiation with distinct peaks corresponding to transitions to excited molecular states which dissociate to specific atomic states of the alkali and halogen atoms. In particular, the inversion and intense superfluorescent emission of the Na resonance line by selective photodissociation of NaI was observed where the fifth harmonic of a Q-switched Nd:YAG laser at 2128 .ANG. was used to photodissociate NaI to the unbound state Na(3p.sup.2 p)+I(5p.sup.5 2 p.sub.3/2).
Although these experimental and theoretical investigations form prior art for both selective photodissociation and anti-Stokes Raman lasers, they do not teach their use for producing the unique results obtained by the present invention.